refactor: wave 2 - split atlas, auto-update-checker, session-recovery, todo-enforcer, background-task hooks

- Extract atlas/ into 15 focused modules (hook, event handler, tool policies, types, etc.)
- Split auto-update-checker into checker/ and hook/ subdirectories with single-purpose files
- Decompose session-recovery into separate recovery strategy files per error type
- Extract todo-continuation-enforcer from monolith to directory with dedicated modules
- Split background-task/tools.ts into individual tool creator files
- Extract command-executor, tmux-utils into focused sub-modules
- Split config/schema.ts into domain-specific schema files
- Decompose cli/config-manager.ts into focused modules
- Rollback skill-mcp-manager, model-availability, index.ts splits that broke tests
- Fix all import path depths for moved files (../../ -> ../../../)
- Add explicit type annotations to resolve TS7006 implicit any errors

Typecheck: 0 errors
Tests: 2359 pass, 5 fail (all pre-existing)

src/hooks/todo-continuation-enforcer/countdown.ts

@@ -0,0 +1,83 @@
+import type { PluginInput } from "@opencode-ai/plugin"
+
+import type { BackgroundManager } from "../../features/background-agent"
+import { log } from "../../shared/logger"
+
+import {
+  COUNTDOWN_SECONDS,
+  HOOK_NAME,
+  TOAST_DURATION_MS,
+} from "./constants"
+import type { ResolvedMessageInfo } from "./types"
+import type { SessionStateStore } from "./session-state"
+import { injectContinuation } from "./continuation-injection"
+
+async function showCountdownToast(
+  ctx: PluginInput,
+  seconds: number,
+  incompleteCount: number
+): Promise<void> {
+  await ctx.client.tui
+    .showToast({
+      body: {
+        title: "Todo Continuation",
+        message: `Resuming in ${seconds}s... (${incompleteCount} tasks remaining)`,
+        variant: "warning" as const,
+        duration: TOAST_DURATION_MS,
+      },
+    })
+    .catch(() => {})
+}
+
+export function startCountdown(args: {
+  ctx: PluginInput
+  sessionID: string
+  incompleteCount: number
+  total: number
+  resolvedInfo?: ResolvedMessageInfo
+  backgroundManager?: BackgroundManager
+  skipAgents: string[]
+  sessionStateStore: SessionStateStore
+}): void {
+  const {
+    ctx,
+    sessionID,
+    incompleteCount,
+    resolvedInfo,
+    backgroundManager,
+    skipAgents,
+    sessionStateStore,
+  } = args
+
+  const state = sessionStateStore.getState(sessionID)
+  sessionStateStore.cancelCountdown(sessionID)
+
+  let secondsRemaining = COUNTDOWN_SECONDS
+  showCountdownToast(ctx, secondsRemaining, incompleteCount)
+  state.countdownStartedAt = Date.now()
+
+  state.countdownInterval = setInterval(() => {
+    secondsRemaining--
+    if (secondsRemaining > 0) {
+      showCountdownToast(ctx, secondsRemaining, incompleteCount)
+    }
+  }, 1000)
+
+  state.countdownTimer = setTimeout(() => {
+    sessionStateStore.cancelCountdown(sessionID)
+    injectContinuation({
+      ctx,
+      sessionID,
+      backgroundManager,
+      skipAgents,
+      resolvedInfo,
+      sessionStateStore,
+    })
+  }, COUNTDOWN_SECONDS * 1000)
+
+  log(`[${HOOK_NAME}] Countdown started`, {
+    sessionID,
+    seconds: COUNTDOWN_SECONDS,
+    incompleteCount,
+  })
+}